Tubular heat exchanger with stress-relieving structure

ABSTRACT

A tubular heat exchanger which has a structure for relieving stresses which otherwise would occur from temperature fluctuations. A plurality of tubes are connected at their opposite ends to a pair of tube plates which in turn are fixed to opposed enlarged end portions of an elongated vessel which surrounds the tubes and which extends between the tube plates. The enlarged end portions of the vessel are flexible and of a sufficient yieldability to absorb stresses which otherwise would occur due to elongation and contraction of the tubes.

United States Patent 1 1 1111 3,822,741 Lippitsch July 9, 11974 TUBULAR HEAT EXCHANGER WITH 2,653,799 9/1953 Stahr et al. 165/83 3,628,507 12/1971 Saporiti 165/134 STRESS-RELIEVING STRUCTURE Josef Lippitseh, Graz, Austria Waagner-Biro Aktiengesellschaft, Vienna, Austria Filed: Mar. 9, 1973 Appl. No.: 339,531

Inventor:

Assignee:

Foreign Application Priority Data Mar. 13, l972 Austria 2075/72 U.S. Cl. 165/83, 165/158 Int. Cl. F28b 7/00 Field of Search 165/158-161, 165/83, 134; 122/32, 34

References Cited UNITED STATES PATENTS 12/1932 Rainey 165/83 X Primary Examiner-Charles J. Myhre Assistant ExaminerTheophil W. Streule, Jr. Attorney, Agent, or Firm-Steinberg & Blake ABSTRACT A tubular heat exchanger which has a structure for relieving stresses which otherwise would occur from temperature fluctuations. A plurality of tubes are connected at their opposite ends to a pair of tube plates which in turn are fixed to opposed enlarged end portions of an elongated vessel which surrounds the tubes and which extends between the tube plates. The enlarged end portions of the vessel are flexible and of a sufficient yieldability to absorb stresses which otherwise would occur due to elongation and contraction of the tubes.

7 Claims, 3 Drawing Figures TUBULAR HEAT EXCHANGER WITH STRESS-RELIEVING STRUCTURE BACKGROUND OF THE INVENTION The present invention relates to heat exchangers.

In particular, the present invention relates to that type of heat exchanger where a plurality of tubes are connected to tube plates between-which there is a vessel which surrounds the tubes for directing a heatexchanging medium along the exterior of the tubes.

With heat-exchangers of this type, during operation of the heat exchanger substantial stresses are encountered due to expansion and contraction which results from temperature fluctuations. These stresses occur at the tubes, the tube plates, and also at the vessel which extends between the tube plates. As a result of these thermal stresses there are failures in the connections between the tubes, the tube plates, and the vessel which surrounds the tubes and is fixed to the tube plates, so that undesirable leakage occurs requiring interruptions in the operation so that the necessary repairs can be made. Thus, up to the present time the stressing of the components resulting from temperature fluctuations creates serious problems which have not yet been satisfactorily solved.

SUMMARY OF THE INVENTION It is accordingly a primary object of the present invention to provide a construction which will avoid the above drawbacks.

In particular, it is an object of the invention to provide a heat exchanger of the above type which is capable of absorbing the stresses occurring from temperature fluctuations in such a way that the operating life of the heat-exchanger will be greatly increased and failure of the components due to thermal stressing will be reliably avoided.

In particular, it is an object of the present invention to provide for a heat-exchanger of the above type an outer vessel which is capable of responding to contraction and elongation of the tubes which are situated within the vessel so as to minimize failures or leakage which might otherwise occur.

Thus, it is a particular object of the present invention to provide for a heat-exchanger of the above type an outer vessel which is capable of automatically compensating for stresses which otherwise would occur.

It is also an object of the present invention to provide a construction of the above type which is capable of operating in such a way that the heat-exchanging medium in the interior of the vessel is uniformly distributed with respect to the exterior of the tubes which are in the vessel.

Furthermore, it is an object of the present invention to provide a construction of the above type which is exceedingly simple and rugged so that it can be utilized at low cost and with great reliability in heat exchangers of the above type.

According to the invention the heat exchanger includes a plurality of tubes and a pair of means which communicate with the tubes for directing a heatexchanging medium therethrough. This pair of means includes a pair of tube plates which are respectively fixed to opposed ends of the tubes. An outer vessel means surrounds the tubes and extends between and is fixed to the tube plates for directing a heat-exchanging medium along the exterior of the tubes. This vessel means has an elongated intermediate portion which is spaced from the tube plates and a pair of opposed end tubes resulting from temperature fluctuations.

BRIEF DESCRIPTION OF DRAWINGS The invention is illustrated by way of example in the accompanying drawings which form part of this application and in which:

FIG. 1 is a schematic longitudinal sectional illustration of a heat exchanger according to the invention;

FIG. 2 is a fragmentary sectional illustration at an enlarged scale as compared to FIG. I showing the structureof the invention at the region of the upper end of FIG. 1 and illustrating the details of the structure with the wall thickness of the components; and

FIG. 3 is a fragmentary schematic illustration of another embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS The heat exchanger of the invention is composed primarily of the heat exchanger tubes 3 which communicate with a pair of means for directing a heat exchanging medium through the interiors of the tubes 3. This pair of means includes a pair of tube plates 6 which are fixed to the opposed ends of the tubes 3 and which are formed with openings which receive the opposed ends of the tubes 3. Thus, these tubes 6 form the ends of a pair of chambers 9 through which a heatexchanging medium is directed in the manner indicated by the arrows 10 of FIG. 1, so that in this way the pair of means 9 serve to direct one of a pair of heatexchanging mediums through the interiors of the tubes 3. Thus, the pair of means 9 form a pair of collecting and distributing chambers which respectively terminate atthe tube plates 6 and which serve to direct the inner heat-exchanging medium along the interiors of the tubes 3 in the direction of the arrows 10.

A vessel means 1, 4 surrounds and contains the tubes 3 and extends between and is fixed to the tube plates 6 in order to direct an outer heat-exchanging medium along the exterior of the tubes 3. This vessel means includes the elongated intermediate portion 4 and a pair of opposed enlarged end portions 1 which have enlarged diameters as compared to the diameter of the intermediate portion 4, these enlarged opposed end portions 1 of the vessel means being directly fixed with the tube plates 6. Thus, the interior ll of the vessel means is defined by the elongated intermediate portion 4 at the opposed ends of which are situated the enlarged portions 1 of the vessel means.

The intermediate portion 4 itself has a pair of opposed elongated end portions 13 which respectively extend into and are surrounded by the enlarged end portions 1, these free end portions 13 being of approximately the same diameter as the remainder of the intermediate portion 4 and terminating at locations spaced from the tube plates 6 so as to define with the latter gaps 5 through which the outer heat-exchanging medium can flow. At their inner ends which are directed toward each other the enlarged end portions 1 have tapered portions 2 which are directly welded to the exterior surface of the intermediate portion 4. Thus, the

gaps form interruptions between the tube plates 6 and the cylindrical part 4 of the outer pressure vessel. The enlarged end portions 1 of the pressure vessel bridge across the gaps 5.

In accordance with a particular feature of the present invention these enlarged end portions 1 respectively have in the regions of the tube plates 6 a flexible construction of sufficient yieldability to permit these enlarged portions 1 to respond to contraction and elongation of the tubes 3 due to temperature fluctuations so that in this way it is possible for stresses, which otherwise would occur in the components, to be absorbed by the enlarged end portions 1 when they yield in response to elongation and contraction of the tubes 3. As is apparent from FIGS. 1 and 2, the enlarged end portions 1 are reduced at their free ends which are fixed to the tube plates 6, respectively. As is shown most clearly in FIG. 2, these reduced ends of the enlarged portions 1 of the vessel means ll, 4 have the configuration of a half shell of a lenticular compensating structure. Thus it will be seen that these reduced portions 7 of the enlargements 1 have a substantially S-shaped cross section and form one half of convolution of a bellows. The smallest diameter of this partial bellows convolution is fixed to the tube plate 6 while the largest diameter thereof is fixed to a cylindrical portion of each enlargement 1. Thus, this compensating structure of lenticular configuration is capable of yielding axially and is of sufficient flexibility so that it will change its configuration and absorb stresses which otherwise would occur due to elongation or contraction of the tubes 3 in response to thermal stresses. Thus, the vessel means 1, 4 is capable of automatically compensating for temperature fluctuations. The inner ends of the enlarged portions I which are distant from the flexible yieldable portions 7 thereof are tapered to form the portions 2 which are directly welded to the intermediate portion 4, as is apparent from FIGS. I and 2.

As is indicated in FIG. 3, instead of forming the vessel means with the reduced portions 7 in the form of one half a bellows convolution which will be of sufficient flexibility and yieldability to absorb the axial stresses which otherwise would occur, several convolutions 7' of a bellows may be provided at each of the enlarged end portions 1 of the vessel means at the region of the tube plates 6. Thus, with this construction shown in FIG. 3 it is also possible for the vessel means to automatically compensate for elongation or contraction of the tubes 3 resulting from temperature fluctuations, the bellows structures 7 readily yielding in order to compensate automatically for elongation and contraction of the tubes 3.

It is to be noted also that the enlarged end portions I are respectively formed with the inlet and outlet openings 14 for the outer heat-exchanging medium, these inlet and outlet openings 14 having the same angular orientation with respect to the axis of the heatexchanger so that they are aligned with each other as is apparent from FIG. 1. Thus, the enlarged opposed end portions 1 of the vessel means also form the chambers through which the outer heat-exchanging medium is introduced into and discharged from the vessel means 1, 4.

As is shown schematically in FIG. 1, the intermediate portion 4 of the vessel means carries in its interior a plurality of baffles 12 which extend transversely across the tubes 3 to provide a uniform distribution of the outer-exchanging medium which flows along the exterior of the tubes 3.

In FIG. 2 the components of FIG. 1 are partially illustrated at an enlarged scale with the reference characters of FIG. 2 also being used in FIG. 1, and FIG. 2 showing the wall thickness of the components. Thus, the intermediate portion 4 of the vessel means has the elongated free end portions 13 which extend into the interior of the enlarged end portions 1. These portions 13 may have a lesser thickness than the remainder of the intermediate portion 4.

As is shown in dotted lines in FIG. 1 and as is illustrated in FIG. 3, it is possible to improve the distribution of the outer heat-exchanging medium which flows in the direction of the arrow 8 of FIG. 2 by providing the elongated free end portions 13 of the intermediate portion 4 with end edges which are situated in oppositely inclined planes in such a way that these end edges are most distant from each other at their portions which are angularly aligned with the inlet and outlet openings 14 and closest to each other at their portions which are most distant from the inlet and outlet openings 14. In this way, the gaps S will have a minimum axial dimension at the region of the inlet and outlets 14 and a gradually increasing axial dimension in a direction away from the inlet and outlet openings 14 so as to improve the distribution of the outer heatexchanging medium.

What is claimed is:

1. In a heat exchanger, a plurality of tubes, a pair of means communicating with said tubes for directing a heat-exchanging medium therethrough, said pair of means respectively including a pair of tube plates respectively fixed to the ends of said tubes, and vessel means surrounding and containing said tubes for directing a heat-exchanging medium along the exterior of said tubes, said vessel means having an elongated intermediate portion situated between and spaced from said tube plates and a pair of opposed end portions which are enlarged as compared to said intermediate portion and which extend from said intermediate portion up to said tube plates, said enlarged opposed end portions of said vessel means respectively having outer ends fixed to said tube plates and inner ends fixed to and surrounding said intermediate portion of said vessel means at the exterior of said intermediate portion, said intermediate portion of said vessel means having a constant diameter and a pair of opposed elongated free end portions which respectively extend into said enlarged opposed end portions of said vessel means beyond the inner ends of the latter toward but terminating short of said tube plates, said enlarged opposed end portions of said vessel means being formed respectively with an inlet and outlet for the heat-exchanging medium which flows along the exterior of said tubes, so that the latter heat-exchanging medium will flow through gaps which are respectively formed between said tube plates and the opposed free end portions of said intermediate vessel portion, said enlarged opposed end portions of said vessel means being flexible and having a sufficient yieldability to respond to contraction and elongation of said tubes resulting from temperature fluctuations so as to reduce stresses which otherwise would occur in said tubes and tube plates.

2. The combination of claim 1 and wherein said enlarged opposed end portions of said vessel means respectively terminating at said tube plates in reduced ends which lower the stiffness of said vessel means at the region of said tube plates and increase the yieldability of said vessel means in an axial direction which is parallel to said tubes.

3. The combination of claim 2 and wherein each of said enlarged end portions of said vessel means has nextto the tube plate to which it is fixed a substantially S- shaped cross section and forming one half of a bellows convolution.

4. The combination of claim 1 and wherein said inlet and outlet for the heat-exchanging medium which flows along the exterior of said tubes are located in alignment with each other respectively at the same locations circumferentially of the pair of opposed enlarged portions of said vessel means, and said opposed free end portions of said intermediate vessel portion which is surrounded by said enlarged end portions respectively terminating in opposed end edges which are respectively situated in oppositely inclined planes with said end edges being situated at their greatest distance from each other in the region of said inlet and outlet and closest to each other at the parts of said end edges which are most distant from said inlet and outlet.

5. The combination of claim 1 and wherein said enlarged opposed end portions of said vessel means respectively have in the region of said tube plates the configurations of a pair of bellows for increasing the flexibility and yieldability of said opposed enlarged end portions of said vessel means in the region of said tube plates.

6. The combination of claim 1 and wherein said opposed free ends of said intermediate portion of said vessel means are situated from each other at least in the region of said inlet and outlet by a distance at least as great as the distance between said inlet and outlet so that the heat exchanging medium entering through said inlet will first engage an outer surface of one of said op posed free ends of said intermediate portion of said vessel means before flowing from the interior of the enlarged end portion of said vessel means which is provided with said inlet around an end edge of said intermediate portion of said vessel means into the interior thereof to flow axially along the exterior of the tubes in said intermediate portion of said vessel means, while the heat-exchanging medium which flows out through said outlet must first flow around the opposite end edge of said intermediate portion of said vessel means before reaching said outlet.

7. The combination of claim 4 and wherein said greatest distance between said end edges is at least as great as the distance between said inlet and outlet so that the heat-exchanging medium entering through said inlet must first flow through the narrowest part of a space defined between the tube plate at the region of said inlet and the adjacent end edge of said intermediate portion of said vessel means while the heatexchanging medium which flows out through said outlet must also first flow through the narrowest part of the space defined between the opposed end edge of said intermediate portion of said vessel means and the adjacent tube plate before reaching said outlet. 

1. In a heat exchanger, a plurality of tubes, a pair of means communicating with said tubes for directing a heat-exchanging medium therethrough, said pair of means respectively including a pair of tube plates respectively fixed to the ends of said tubes, and vessel means surrounding and containing said tubes for directing a heat-exchanging medium along the exterior of said tubes, said vessel means having an elongated intermediate portion situated between and spaced from said tube plates and a pair of opposed end portions which are enlarged as compared to said intermediate portion and which extend from said intermediate portion up to said tube plates, said enlarged opposed end portions of said vessel means respectively having outer ends fixed to said tube plates and inner ends fixed to and surrounding said intermediate portion of said vessel means at the exterior of said intermediate portion, said intermediate portion of said vessel means having a constant diameter and a pair of opposed elongated free end portions which respectively extend into said enlarged opposed end portions of said vessel means beyond the inner ends of the latter toward but terminating short of said tube plates, said enlarged opposed end portions of said vessel means being formed respectively with an inlet and outlet for the heat-exchanging medium which flows along the exterior of said tubes, so that the latter heat-exchanging medium will flow through gaps which are respectively formed between said tube plates and the opposed free end portions of said intermediate vessel portion, said enlarged opposed end portions of said vessel means being flexible and having a sufficient yieldability to respond to contraction and elongation of said tubes resulting from temperature fluctuations so as to reduce stresses which otherwise would occur in said tubes and tube plates.
 2. The combination of claim 1 and wherein said enlarged opposed end portions of said vessel means respectively terminating at said tube plates in reduced ends which lower the stiffness of said vessel means at the region of said tube plates and increase the yieldability of said vessel means in an axial direction which is parallel to said tubes.
 3. The combination of claim 2 and wherein each of said enlarged end portions of said vessel means has next to the tube plate to which it is fixed a substantially S-shaped cross section and forming one half of a bellows convolution.
 4. The combination of claim 1 and wherein said inlet and outlet for the heat-exchanging medium which flows along the exterior of said tubes are located in alignment with each other respectively at the same locations circumferentially of the pair of opposed enlarged portions of said vessel means, and said opposed free end portions of said intermediate vessel portion which is surrounded by said enlarged end portions respectively terminating in opposed end edges which are respectively situated in oppositely inclined planes with said end edges being situated at their greatest distance from each other in the region of said inlet and outlet and closest to each other at the parts of said end edges which are most distant from said inlet and outlet.
 5. The combination of claim 1 and wherein said enlarged opposed end portions of said vessel means respectively have in the region of said tube plates the configurations of a pair of bellows for increasing the flexibility and yieldability of said opposed enlarged end portions of said vessel means in the regioN of said tube plates.
 6. The combination of claim 1 and wherein said opposed free ends of said intermediate portion of said vessel means are situated from each other at least in the region of said inlet and outlet by a distance at least as great as the distance between said inlet and outlet so that the heat exchanging medium entering through said inlet will first engage an outer surface of one of said opposed free ends of said intermediate portion of said vessel means before flowing from the interior of the enlarged end portion of said vessel means which is provided with said inlet around an end edge of said intermediate portion of said vessel means into the interior thereof to flow axially along the exterior of the tubes in said intermediate portion of said vessel means, while the heat-exchanging medium which flows out through said outlet must first flow around the opposite end edge of said intermediate portion of said vessel means before reaching said outlet.
 7. The combination of claim 4 and wherein said greatest distance between said end edges is at least as great as the distance between said inlet and outlet so that the heat-exchanging medium entering through said inlet must first flow through the narrowest part of a space defined between the tube plate at the region of said inlet and the adjacent end edge of said intermediate portion of said vessel means while the heat-exchanging medium which flows out through said outlet must also first flow through the narrowest part of the space defined between the opposed end edge of said intermediate portion of said vessel means and the adjacent tube plate before reaching said outlet. 